Method of photographic recording by an electric field



July 4, 1967 A SCHWERTZ ET AL 3,329,961

METHOD OF PHOTOGRAPHIC RECORDING BY AN ELECTRIC FIELD Filed Jan. 9, 1965 CONTROL SYSTEM I .MHII

\ ATTORNEXJ United States Patent ()fifice 3,329,951 Patented July 4, 1967 3,329,961 METHOD OF PHOTOGRAPHIC RECORDING BY AN ELECTRIC FIELD Frederick A. Schwertz and Robert A. Wilferth, Pittsford, N.Y., assignors, by nlesne assignments, to Technical Operations, Incorporated, a corporation of Delaware Filed Jan. 9, 1963, Ser. No. 250,983 Claims. (Cl. 346-74) The present invention relates to the area of electrical recording. In particular the present invention is concerned with recording on silver halide photographic materials by means of electrical energy, and is a continuation in part of our copending application S.N. 220,992, filed Sept. 4, 1962, now abandoned, entitled Electrical Recording.

It has heretofore been recognized that optically responsive silver halide photographic materials are also responsive to electrical energy, and may be used to record information patterns presented electrically to the surface thereof. In particular, as set forth in greater detail in US. Patent 2,978,968, issued Apr. 11, 1961, to F. A. Schwertz, photographic film may be interposed between a pair of closely spaced electrodes, and a field discharge initiated between the electrodes creates a latent image on the film by means of an ion current flow across the gap. The latent image may then be developed by a conventional photographic developing process into a visible record. In this system, a first electrode which may be designated as a character electrode, is spaced from the photosensitive emulsion surf-ace of the silver halide material by a small air gap, and the back of the film is positioned against a second, or backing or ground electrode. The first electrode may be in the shape of an alpha-numeric or other character, or it may be -a one or two-dimensional array of point electrodes adapted to be selectively energized in a desired informational pattern or sequence. The object of the discharge from the first electrode across the small air gap to the silver halide emulsion is to form a photographic latent image of the energized character electrode on'the film which is subsequently developed into visible form. In order to obtain optimum definition of the image of the energized character electrode on the film, it is preferred that the field discharge from the character electrode across the air gap to the photographic film be in the silent invisible field discharge range. It is also preferable that this air gap be very small, such as of the order of several thousandths of an inch.

The present invention embodies an improvement in this area of electrical recording on silver halide photographic materials by elfecting such recordings with much less energy than has heretofore been possible, and by effecting when desired directly visible print out images without development. In accordance with the present invention, the recording is effected on a particular type of silver halide photographic material, namely one comprising a layer of silver halide micro-crystals which are supported upon a substrate primarily by being bound directly to the substrate and directly to each other, as distinguished from being carried in an emulsion vehicle. Such photographic layers may be, and preferably are formed by vacuum evaporation of silver halide, such as silver bromide, with or without silver iodide and/ or silver chloride, and condensation of the halide vapors on a suitable photographic quality substrate, such as baryta paper, a terephthalate film such as Cronar, or a suitable photographic quality acetate film. The silver halide microcrystals thus formed are supported on the substrate by being bound directly thereto and to each other. Although it is not essential for purposes of the present invention, if desired, the silver halide layer may be sensitized with suitable silver halide photographic sensitizers.

When such a photographic material is exposed to a silent and invisible electrical field in the manner above suggested, it is found that a latent image of the character electrode is obtained with an exposure energy of a number of orders of magnitude less than that required for an equivalent image on conventional photographic emulsion silver halide film, when the two materials have approximately equal optical photographic sensitivity. Indeed, the present photographic film is so sensitive to electrical field energy that direct print out images of the character electrode can be obtained without development.

It is accordingly one object of the present invention to provide for the electrical recording of intelligence by electrical field energy, on a photographic layer of silver halide micro-crystals wherein the silver halide crystals are supported on a substrate primarily by being bound directly to the substrate and directly to each other.

Another object of the present invention is to provide for such electrical recording of intelligence, wherein said silver halide layer is formed by vacuum evaporation of the silver halide onto the substrate.

Another object of the present invention is .to provide for the electrical recording of a chemically developable latent intelligence image by electrical field energy, on a photographic layer of silver halide micro-crystals wherein the silver halide crystals are supported on a substrate primarily by being bound directly to the substrate and directly to each other.

And still another object of the present invention is to provide for the electrical recording of a print out intelligence image by electrical field energy, on a photographic layer of silver halide micro-crystals wherein the silver halide crystals are supported on a substrate primarily by being bound directly to the substrate and directly to each other.

Other objects and advantages of the present inven-.

tion will become apparent to those skilled in the art from a consideration of the following detailed description of exemplary specific embodiments thereof, had in conjunction with the accompanying drawings wherein like reference characters refer to like or corresponding parts, and wherein:

FIG. 1 is a schematic view of -a system for elfecting electrical field energy recording on a web of photographic material;

FIG. 2 is an enlarged, fragmentary detailed view of a character electrode disk and backing or ground electrode, as employed in FIG. 1;

FIG. 3 is a perspective view of a character electrode in the form of a two-dimensional array of point or pin elements, for use in the system of FIG. 1 in place of the character electrode disk; and

FIG. 4 is a cross-sectional view of the electrode of FIG. 3 taken along the line 3-3, in combination with a backing electrode, and showing a fragment of photographic web passing therebetween.

As previously stated, the photographic material employed in the practice of the present invention comprises a layer of silver halide crystals carried by a substrate, wherein the crystals are primarily bound directly to the substrate and directly to each other. Preferably, this photographic material is fabricated by evaporating the silver halide under a high vacuum and depositing the vapors thereof upon a suitable photographic substrate. Preferably the silver halide is silver bromide, with or without small amounts of other silver halides such as silver chloride and/or silver iodide. The substrate may be any suitable photographic quality base material, such as baryta paper, a terephthalate film, or an acetate film. However, for the purpose of illustration herein, the particular photographic material employed is silver bromide evaporated at a temperature of approximately 600-650 C., under a pressure of about 10- to 10* mm. of Hg, and deposited upon photographic quality baryta paper. This photographic paper may of course be prepared in webs of indefinite length by passing the paper web incrementally through the silver bromide evaporation zone, whereby a layer of silver bromide crystals is caused to be deposited uniformly over the extent of the web.

The resultant web of evaporation deposited silver halide paper may be utilized in an electrical recording system such as is schematically illustrated in FIG. 1 wherein the paper is fed from a supply roll 11, past the electrical recording station 12, into a conventional photographic chemical developing and fixing station 13, whereupon the paper may be passed through a viewing station or area 14, and/ or collected on storage roll 15.

The electrical recording station 12 is shown as comprising a character electrode disk 21 having a plurality of character electrodes 22 located about its periphery. Disk 21 is rotated on its axis 23 for the purpose of bringing desired electrodes 22 in closely spaced juxtaposition to backing or ground electrode 24, While the photographic paper 10 is moved past the recording station. A control system 25 is provided for selecting a desired sequence of electrodes 22 to be positioned opposite the ground electrode 24 in accordance with a prescribed intelligence input to the system. Thus, if for example, the electrodes 22 are alpha-numeric characters, a desired message may be recorded on the photographic web 10 as selected characters are positioned opposite the ground electrode 24, While the web 10 is advanced in synchronism therewith. The advance of web 10 is of course preferably keyed to the rate of positioning electrodes 22 in recording position, and is therefore preferably an intermittent feed or advance. As each selected character electrode is positioned for recording by control system 25, the control system thereupon electrically pulses the character electrodes from power source 26 to create a suitable electrical field between the selected character electrode 22 and the backing electrode 24, and thereby effect a recording of the image of the selected character electrode on a section of photographic web 10.

If the energy of the electrical field is sufficient only to establish a latent image on the web 10, the web is subsequently passed through a conventional photographic developing and fixing station 13, where the latent image is developed into a visible image. Thereafter, the recorded image may be viewed as the web emerges from the developing and fixing station, and/or the emerging web can be dried and then stored on roll 15.

With reference to FIG. 2, each of the character electrodes 22 comprises a block of dielectric material 33 mounted on the periphery of disk 21, but provided with a fiat planar outer face 35. A conductive character element 34, having for example an alpha-numeric shape, is imbedded in block 33, but projects slightly from the surface thereof. The surface of conductive element 34 is also machined or otherwise formed to lie in a flat plane. The conductive element 34 is of course electrically connected for energization from power source 26.

Ground or backing plate 24 is formed of conductive material, and it too is provided with a back section 36 adapted to lie in a flat plane parallel with the plane of the surface of conductive element 34 when the latter is in position for recording. Side flanges 31 extend forwardly from back section 36 and may overlap slightly the sides of block 33. Inwardly facing grooves or channels 32 are formed in each side flange 31 to provide guideways for the photographic Web 10 as it passes through the recording station 12.

Electrode disk 21 and ground electrode 24 are care fully positioned relative to each other, so that in operation, when photographic Web 10 is located and fed in guide channels 32, the surface of character element 34 is spaced from the adjacent surface of Web 10 by a slight air gap. The selection of this air gap is important in order to obtain an adequate electrical field effect with good character definition on web 10. It has been found that good character definition can be obtained when the photographic sensitive surface of web 10, i.e., the surface having the silver halide coating thereon, is positioned toward or facing the character electrode, and the air gap is about 0.004 of an inch.

In place of the character electrode disk 21 and its peripheral character electrodes 22, one may employ an electrode 40 formed of an array of point orpin conductive elements 43, such as shown in FIG. 3. This electrode comprises a dielectric block 41 supported by a housing 42, and having a two-dimensional array of point electrode elements 43 embedded in the dielectric base 41. Point or pin electrode elements 43 projects slightly from the surface of block 41, and their projecting ends are located to lie in a single flat plane. An electrical lead is connected to each electrode element 43, and these leads emerge from the back of housing 42 to form cable 44. Electrode array 40 is combined with backing or ground electrode 24 in the same manner as the individual electrodes 22 of disk 21, to be properly spaced from a photographic web 10 passing therebetween for electrical field energy recording.

In this instance, instead of mechanically moving an array of individual character electrodes selectively into recording position, selected groups of the point electrode elements are energized through a suitable selection control network to define, for example, a sequence of desired alpha-numeric characters and record the same sequentially on the web 10. Since with the two-dimensional pin electrode element array a complete character is formed with each operation, the web 10 should be advanced stepby-step, one step for each record character, in synchromism with each character energization. Alternatively, it is apparent that instead of the two-dimensional array, a one-dimensional array of point or pin elements could be employed, i.e., a single line of conductive point elements. In this instance, the movement of web 10 could be continuous rather than intermittent as the selective energization of the line of electrode elements is continuously varied to accord with the input intelligence thereto, to record the same on the web 10. This latter alternative of course permits the recordation of pictorial information and is not confined to pre-established character forms such as is particularly the case of the electrode disk of FIG. 2. Also, if desired, for certain recording purposes a single point or pin electrode could be employed and the intelligence applied thereto in the form of a varying amplitude signal, while the web 10 is continuously moved past that pin. Such a system would provide a single line trace on web 10 of density denoted intelligence.

In order to illustrate further the present invention by way of specific example, recordings have been obtained on evaporated silver bromide paper, wherein the silver bromide was evaporated onto a baryta paper base under a vacuum of about 4.5 1O- mm. of Hg, and at a temperature of about 620625 C., to a thickness of about .2 to .3 micron. Samples of this photographic paper were tested and found to have an optical photographic speed of about 0.03 ASA. This paper was then positioned between a backing electrode and a character electrode of the type illustrated in FIG. 2, with the paper base in contact with the backing electrode and the silver bromide layer facing the character electrode. The air gap between the surface of the silver bromide layer and the surface of the character electrode was about 0.004 of an inch. A 1400 volt pulse was impressed across the two electrodes for about 100 microseconds, with the character electrode being negative. As a result, a short duration current pulse of about 40 microseconds was observed to flow between the electrodes. Upon conventional chemical development of the thus exposed photographic paper, a well defined image of the character electrode was rendered clearly visible. The above-mentioned current pulse contained a charge of about 1.5 X coul-ombs/ sq. mm. of image.

Using the same silver bromide photographic paper as in the preceding example, a sample of the paper was similarly exposed to a character electrode electrical field resulting from the application of about a 1400 volt source across the electrodes for 30 seconds. A steady state current of about 0.2 microampere was observed to flow from this energization. As a result, a well defined clearly visible image of the character electrode was printed out on the silver bromide paper directly from the field energy without chemical development.

To demonstrate the remarkable speed or response of the evaporated silver bromide paper to this electrical field energy, conventional comparable gelatin emulsion silver halide photographic paper samples were similarly exposed to the field under substantially identical conditions. One such sample was a gelatin paper known as Industro 4, contrast 4 contact paper, having an optical photographic speed of about 0.01 ASA. When this sample was exposed as above to the character electrode field, energized by the application of about a 1400 volt source across the electrodes for 30 seconds, only after chemical development did a clearly visible image of the character electrode appear. This image was comparable to that obtained with only a 100 microsecond exposure, as above described with respect to the evaporated silver bromide paper. Another sample tested was a silver halide gelatin paper known as Fast Record B photocopy paper, having an optical photographic speed of about 3 ASA. This sample, when similarly exposed as above, required an electrical field exposure from a 1400 volt source of electrode energization of about 2 seconds, to produce, on chemical development, an image comparable to that obtained in the above-described 100 microsecond exposure. Still another example of the remarkable and unexpected response of the evaporated silver halide photographic material to electrical field energy may be cited. Using a sample of the evaporated silver bromide paper prepared as above-described, it was positioned between a pin electrode element and a backing electrode, as illustrated for example in FIG. 4, except a single pin 43 was utilized instead of the two-dimensional array. The spacing between electrodes was about 0.002 of an inch, and the pin electrode element had a tip radius of about 0.2 mm. The photographic paper was inserted between the electrodes with its silver bromide surface facing the pin electrode element. With the pin electrode element negative, it was found that a 1400 volt pulse need be impressed across the two electrodes for only about 0.8 microsecond in order to obtain, after chemical development of the exposed paper, an image of the pin electrode element comparable to that obtained in the preceding examples.

Thus, from the foregoing specific embodiments and examples of the present invention it will be appreciated that there is provided a new process of electrical field energy recording employing as the recording medium a photographic layer of silver halide micro-crystals on a substrate, wherein the silver halide micro-crystals are supported on the substrate primarily by being bound directly to the substrate and directly to each other. The speed of recording by this process is a number of orders of magnitude greater than is obtained using conventional gelatin photographic silver halide materials of comparable optical speeds. However, it is not intended that the present invention shall be considered as limited to the described specific embodiments or examples, for various modifications and variations thereof will be apparent to those skilled in the art, and such variations and modifications as are embraced by the spirit and scope of the appended claims are contemplated as within the purview of the present invention.

What is claimed is:

1. A method of recording comprising generating a silent and invisible electric field in an intelligence denotative pattern, and exposing thereto a photographic material having a layer of silver halide micro-crystals on a substrate, wherein the silver halide crystals are supported on the substrate primarily by being bound directly thereto and directly to each other, to record said pattern on said material.

2. A method as set forth in claim 1, wherein said silver halide is primarily silver bromide.

3. A method as set forth in claim 2, wherein said silver bromide layer is formed on said substrate by evapration of silver bromide under high vacuum conditions and condensation of the silver bromide vapor on said substrate.

4. A method as set forth in claim 1, wherein said material is exposed to said field with said layer facing the negative electrode.

5. A method as set forth in claim 4, wherein said negative electrode comprises a conductive element in the shape of a specific intelligence denotative character.

6. A method as set forth in claim 4, wherein said negative electrode comprises a plurality of electrically conductive pin elements arranged in an array for selective energization.

7. A method of recording as set forth in claim 4, wherein the spacing between said negative electrode and said layer is not greater than about several thousandths of an inch.

8. A method as set forth in claim 1, wherein the rec- 'ord impressed on said material by said field is in the form of a latent image, and said method further includes the step of developing said latent image to a visible image.

9. A method of recording comprising applying a voltage across a pair of spaced electrodes of a magnitude to create a silent and invisible electrical field therebetween, forming the field into an intelligence denotative pattern, and interposing between said electrodes a photographic medium having a layer of silver halide microcrystals on a substrate, wherein the silver halide microcrystals are supported on the substrate primarily by being bound directly to the substrate and directly to each other, to record said pattern on said material.

10. A method as set forth in claim 9, wherein said forming step is effected by means of a conductive element on one of said electrodes having the shape of a specific intelligence denotative character.

11. A method as set forth in claim 9, wherein said forming step is effected by means of a plurality of electrically conductive pin elements arranged in an array for selective energization.

12. A method of recording comprising applying voltage signals across a pair of spaced electrodes of a magnitude to create a silent and invisible electrical field therebetween, forming successive selected field patterns denotative of successive bits of intelligence, passing a web of a photographic medium between said electrodes in keyed relation to said successive field patterns to expose successive areas of said web to said selected patterns torecord said patterns on said web, said photographic medium comprising a layer of silver halide micro-crystals on a substrate wherein the silver halide micro-crystals are supported on the substrate primarily 7 by being bound directly to the substrate and directly to each other.

13. A method as set forth in claim 12, wherein the record impressed on said material by said field is in the form of a latent image, and said method further includes the step of developing said latent image to a visible image.

14. A method as set forth in claim 13, wherein said forming step is effected by means of a conductive element on one of said electrodes having a fixed shape denotative of a specific intelligence bit.

15. A method as set forth in claim 13, wherein said forming. step is effected by means of a plurality of electrically conductive pin elements arranged in an array for selective energization.

References Cited UNITED STATES PATENTS 2,978,962; 4/1961 Schwertz 346-74 BERNARD KONICK, Primary Examiner.

1O IRVING L. SRAGOW, T. W. FEARS,

Assistant Examiners. 

1. A METHOD OF RECORDING COMPRISING GENERATING A SILENT AND INVISIBLE ELECTRIC FIELD IN AN INTELLIGENCE DENOTATIVE PATTERN, AND EXPOSING THERETO A PHOTOGRAPHIC MATERIAL HAVING A LAYER OF SILVER HALIDE MICRO-CRYSTALS ON A SUBSTRATE, WHEREIN THE SILVER HALIDE CRYSTALS ARE SUPPORTED ON THE SUBSTRATE PRIMARILY BY BEING BOUND DIRECTLY THERETO AND DIRECTLY TO EACH OTHER, TO RECORD SAID PATTERN ON SAID MATERIAL. 